Method of and Apparatus for Inspecting Semiconductor Device
1. Field of the Invention
The present invention relates to a method of and an apparatus for inspecting a semiconductor device, and more particularly to a method thereof and an apparatus therefor used to inspect whether or not there occurs an opening failure of a contact hole formed in a semiconductor wafer by observing a secondary electron image obtained through irradiation with a charged particle beam.
2. Description of the Background Art
Two methods has been conventionally used to inspect whether a contact hole formed in a semiconductor wafer is opened/not-opened. One of them is shown in a conceptional view of FIG. 16. The method uses a defect inspection device 100 and a charged-particle beam device 101. First, the defect inspection device 100 is used for inspection. After that, the charged-particle beam device 101 inputs defect inspection data D100 therein from the defect inspection device 100 and observes a contact hole which seems to have an opening failure.
In another method, whether a contact hole is opened/not-opened is judged by measuring the hole diameter of the contact hole with a CD-SEM and the like.
The former method in the background art, however, has the following problems; the apparatus necessarily becomes large as a whole since the defect inspection device is needed, and moreover it takes long time to perform the inspection since the defect inspection by the defect inspection device and the observation of the defective portion by the charged-particle beam device are separately performed.
The later method in the background art has a problem of low reliability of inspection as compared with the former method since whether the contact hole is opened/not-opened is judged only by measuring the hole diameter, not by direct inspection on whether the contact hole is actually opened or not.
The present invention is directed to a method of inspecting a semiconductor device. According to a first aspect of the present invention, in the method, one of semiconductor wafers each provided with a plurality of holes is mounted on a stage as a semiconductor wafer under inspection, and assuming that small regions obtained by sectioning a wafer surface of the semiconductor wafer under inspection into a plurality of regions are defined as inspection regions, each of the inspection regions is irradiated with charged particles from a charged-particle irradiation unit and a secondary electron image obtained by irradiation with the charged particles is observed, to inspect whether or not there occurs an opening failure in the holes inside each of the small regions, and the method of the first aspect comprises the steps of: (a) inputting positional data on at least one specified small region to a control unit, the at least one specified small region being likely to have the opening failure than the others of the small regions in the wafer surface; and (b) inspecting whether or not there occurs the opening failure in the at least one specified small region while the control unit relatively moves the charged-particle irradiation unit and the stage on the basis of the positional data so that the at least one specified small region is irradiated with the charged particles.
According to a second aspect of the present invention, in the method according to the first aspect, the step (a) includes the steps of: (a-1) inputting design data of the semiconductor wafers to an inspection-region determination unit; and (a-2) identifying the at least one specified small region on the basis of the design data by the inspection-region determination unit.
According to a third aspect of the present invention, in the method according to the first aspect, the step (a) includes the steps of: (a-1) inputting a defective distribution in the wafer surface obtained on a plurality of products already manufactured by using chips obtained from the other semiconductor wafers having the same structure as the semiconductor wafer under inspection to an inspection-region determination unit; and (a-2) identifying a specified region in the wafer surface, which is likely to have a defective, on the basis of the defective distribution by the inspection-region determination unit, to determine the small region corresponding to the specified region as the specified small region.
According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, the at least one specified small region includes a plurality of specified small regions, and the method further comprises the steps of: (c) storing inspection results obtained through the method of inspection into a database; and (d) identifying a failure high-incidence region at which occurrence of the opening failure is found in a plurality of semiconductor wafers among the plurality of specified small regions while the control unit refers to the database, and in the method of the fourth aspect, inspection on whether or not there occurs the opening failure is made only on the failure high-incidence region in the step (b).
According to a fifth aspect of the present invention, in the method of inspecting a semiconductor device, one of semiconductor wafers each provided with a plurality of holes is mounted on a stage as a semiconductor wafer under inspection, and assuming that small regions obtained by sectioning a wafer surface of the semiconductor wafer under inspection into a plurality of regions are defined as inspection regions, each of the inspection regions is irradiated with charged particles from a charged-particle irradiation unit and a secondary electron image obtained by irradiation with the charged particles is observed, to inspect whether or not there occurs an opening failure in the holes inside each of the small regions, and the method comprises the steps of: (a) storing inspection results obtained through the method of inspection into a database; (b) identifying a failure high-incidence region at which occurrence of the opening failure is found in a plurality of semiconductor wafers among the plurality of small regions while a control unit refers to the database; and (c) inspecting whether or not there occurs the opening failure in the failure high-incidence region while the control unit relatively moves the charged-particle irradiation unit and the stage so that the failure high-incidence region is irradiated with the charged particles in the semiconductor wafer under inspection.
According to a sixth aspect of the present invention, in the method according to any one of the first to fifth aspects, the plurality of holes include a plurality of the holes belonging to a first group and a plurality of the holes belonging to a second group which are different from each other in intensity of secondary electrons generated from surfaces of the holes by irradiation with the charged particles even when there occurs no opening failure, and the step (b) includes the steps of: (b-1) grouping the plurality of holes included in the at least one specified small region into the holes belonging to the first group and the holes belonging to the second group; (b-2) inspecting whether or not there occurs the opening failure in the holes belonging to the first group; and (b-3) inspecting whether or not there occurs the opening failure in the holes belonging to the second group, the step (b-3) being separately performed from the step (b-2).
The present invention is also directed to an apparatus for inspecting a semiconductor device. According to a seventh aspect of the present invention, the apparatus comprises: a stage on which one of semiconductor wafers each provided with a plurality of holes is mounted as a semiconductor wafer under inspection; a charged-particle irradiation unit for irradiating one of inspection regions with charged particles, the inspection regions being small regions obtained by sectioning a wafer surface of the semiconductor wafer under inspection into a plurality of regions; a failure judgment unit for judging whether or not there occurs an opening failure in the holes inside each of the small regions by observing a secondary electron image obtained by irradiation with the charged particles; and a control unit for relatively moving the charged-particle irradiation unit and the stage on the basis of positional data on a specified small region which is more likely to have the opening failure than the others of the small regions in the wafer surface so that the specified small region is irradiated with the charged particles.
According to an eighth aspect of the present invention, the apparatus according to the seventh aspect further comprises an inspection-region determination unit for identifying the specified small region on the basis of design data on the semiconductor wafer under inspection.
According to a ninth aspect of the present invention, the apparatus according to the seventh aspect further comprises an inspection-region determination unit for identifying a specified region in the wafer surface, which is likely to have a defective, on the basis of a defective distribution in the wafer surface obtained on a plurality of products already manufactured by using chips obtained from the other semiconductor wafers having the same structure as the semiconductor wafer under inspection, to determine the small region corresponding to the specified region as the specified small region.
According to a tenth aspect of the present invention, the apparatus according to any one of the seventh to ninth aspects further comprises a database storing inspection results obtained by using the apparatus for inspection, which can be referred to by the control unit.
According to an eleventh aspect of the present invention, the apparatus for inspecting a semiconductor device comprises: a stage on which one of semiconductor wafers each provided with a plurality of holes is mounted as a semiconductor wafer under inspection; a charged-particle irradiation unit for irradiating one of inspection regions with charged particles, the inspection regions being small regions obtained by sectioning a wafer surface of the semiconductor wafer under inspection into a plurality of regions; and a failure judgment unit for judging whether or not there occurs an opening failure in the holes inside each of the small regions by observing a secondary electron image obtained by irradiation with the charged particles, and the apparatus of the eleventh aspect further comprises: a database storing inspection results obtained by using the apparatus for inspection; and a control unit for identifying a failure high-incidence region at which occurrence of the opening failure is found in a plurality of semiconductor wafers among a plurality of small regions by referring to the database and relatively moving the charged-particle irradiation unit and the stage so that the failure high-incidence region is irradiated with the charged particles in the semiconductor wafer under inspection.
According to a twelfth aspect of the present invention, in the apparatus according to any one of the seventh to eleventh aspects, the plurality of holes include a plurality of the holes belonging to a first group and a plurality of the holes belonging to a second group which are different from each other in intensity of secondary electrons generated from surfaces of the holes by irradiation with the charged particles even when there occurs no opening failure, and the failure judgment unit has a hole grouping unit for grouping the plurality of holes included in the specified small region into the holes belonging to the first group and the holes belonging to the second group.
The method of inspecting a semiconductor device of the first aspect of the present invention ensures reduction in time needed for the inspection as compared with the background-art semiconductor-device inspection method using a defect inspection device. Further, the method of the first aspect enhances reliability of the inspection as compared with the background-art semiconductor-device inspection method in which judgment is made on whether or not the contact hole is opened/not-opened only by measuring the hole diameter. Furthermore, since the inspection is made not on all the inspection regions, it is possible to reduce the time needed for the inspection as compared with the inspection method in which the inspection is made on all the inspection regions. Moreover, since the inspection is always performed on the specified small region with strong possibility of having the opening failure of the contact hole, it is possible to efficiently detect occurrence of the opening failure.
In the method of the second aspect of the present invention, to determine the specified small region to be inspected, an operator teaches nothing but the inspection-region determination unit automatically identifies the specified small region on the basis of the design data of the semiconductor wafer under inspection. Therefore, it is possible to achieve automatization of the inspection and ensure uniformization of inspection accuracy.
In the method of the third aspect of the present invention, to determine the specified small region to be inspected, the operator teaches nothing but the inspection-region determination unit automatically determines the specified small region on the basis of the defective distribution. Therefore, it is possible to achieve automatization of the inspection and ensure uniformization of inspection accuracy. Moreover, by referring to the defective distribution obtained on actual products, it is possible to determine the specified small region with consideration to total causes of failure including processing problems as well as the structural problems.
In the method of the fourth aspect of the present invention, after the inspection on a plurality of semiconductor wafers is completed and respective inspection results on the specified small regions are stored in the database, instead of all the specified small regions, only the failure high-incidence regions at each of which occurrence of the opening failure is found in a plurality of semiconductor wafer are inspected. Therefore, it is possible to further reduce the time needed for inspection and further enhance the efficiency of inspection.
In the method of the fifth aspect of the present invention, after the inspection on a plurality of semiconductor wafers is completed and the inspection results thereof are stored in the database, instead of all the specified small regions, only the failure high-incidence regions at each of which occurrence of the opening failure is found in a plurality of semiconductor wafer are inspected. Therefore, it is possible to further reduce the time needed for inspection and further enhance the efficiency of inspection.
In the method of the sixth aspect of the present invention, since the inspection can be made by the group of the holes which are connected to the portions having the same electric capacity, it is possible to avoid an inspection error due to difference in electric capacity.
The apparatus for inspecting a semiconductor device of the seventh aspect of the present invention ensures simplification of constitution and reduction in time needed for the inspection as compared with the background-art semiconductor-device inspection apparatus using a defect inspection device. Further, the apparatus of the seventh aspect enhances reliability of the inspection as compared with the background semiconductor-device inspection apparatus which makes judgment on whether or not the contact hole is opened/not-opened only by measuring the hole diameter. Furthermore, since the inspection is made not on all the inspection regions, it is possible to reduce the time needed for the inspection as compared with the inspection apparatus which makes the inspection on all the inspection regions. Moreover, since the inspection is always performed on the specified small region with strong possibility of having the opening failure of the contact hole, it is possible to efficiently detect occurrence of the opening failure.
In the apparatus of the eighth aspect of the present invention, to determine the specified small region under inspection, an operator teaches nothing but the inspection-region determination unit automatically identifies the specified small region on the basis of the design data of the semiconductor wafer under inspection. Therefore, it is possible to achieve automatization of the inspection and ensure uniformization of inspection accuracy.
In the apparatus of the ninth aspect of the present invention. to determine the specified small region to be inspected, the operator teaches nothing but the inspection-region determination unit automatically identifies the specified small region on the basis of the defective distribution. Therefore, it is possible to achieve automatization of the inspection and ensure uniformization of inspection accuracy. Moreover, by referring to the defective distribution obtained on actual products, it is possible for the inspection-region determination unit to determine the specified small region with consideration to total causes of failure including problems in the process as well as the structural problems.
In the apparatus of the tenth aspect of the present invention, the control unit can identify the failure high-incidence region at which occurrence of opening failure is found in a plurality of semiconductor wafers among the specified small regions by referring the database. Therefore, since only the failure high-incidence regions are inspected, instead of all the specified small regions, after the inspection on a plurality of semiconductor wafers is completed and the inspection results thereof are stored in the database, it is possible to further reduce the time needed for inspection and further enhance the efficiency of inspection.
In the apparatus of the eleventh aspect of the present invention, since only the failure high-incidence regions are inspected, instead of all the specified small regions, after the inspection on a plurality of semiconductor wafers is completed and the inspection results thereof are stored in the database, it is possible to further reduce the time needed for inspection and further enhance the efficiency of inspection.
In the apparatus of the twelfth aspect of the present invention, the inspection on the holes belonging to the first group and the inspection on the holes belonging to the second group can be separately performed, and it is thereby possible to avoid an inspection error due to difference in electric capacity.
An object of the present invention is to provide a method of and an apparatus for inspecting a semiconductor device, with a simpler constitution using no defect inspection device, requiring a short time for inspection and ensuring high reliability in inspecting whether a contact hole formed in a semiconductor wafer is opened/not-opened.